The invention relates to systems and methods for ablating myocardial tissue for the treatment of cardiac conditions.
Physicians make use of catheters today in medical procedures to gain access into interior regions of the body to ablate targeted tissue areas. It is important for the physician to be able to precisely locate the catheter and control its emission of energy within the body during tissue ablation procedures.
For example, in electrophysiological therapy, ablation is used to treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician places an ablating element carried on the catheter near the cardiac tissue that is to be ablated. The physician directs energy from the ablating element to ablate the tissue and form a lesion.
In electrophysiological therapy, there is a growing need for ablating elements capable of providing lesions in heart tissue having different geometries.
For example, it is believed the treatment of atrial fibrillation requires the formation of long, thin lesions of different curvilinear shapes in heart tissue. Such long, thin lesion patterns require the deployment within the heart of flexible ablating elements having multiple ablating regions. The formation of these lesions by ablation can provide the same therapeutic benefits that the complex suture patterns that the surgical maze procedure presently provides, but without invasive, open heart surgery.
As another example, it is believed that the treatment of atrial flutter and ventricular tachycardia requires the formation of relatively large and deep lesions patterns in heart tissue. Merely providing xe2x80x9cbiggerxe2x80x9d electrodes does not meet this need. Catheters carrying large electrodes are difficult to introduce into the heart and difficult to deploy in intimate contact with heart tissue. However, by distributing the larger ablating mass required for these electrodes among separate, multiple electrodes spaced apart along a flexible body, these difficulties can be overcome.
With larger and/or longer multiple electrode elements comes the demand for more precise control of the ablating process. The delivery of ablating energy must be governed to avoid incidences of tissue damage and coagulum formation. The delivery of ablating energy must also be carefully controlled to assure the formation of uniform and continuous lesions, without hot spots and gaps forming in the ablated tissue.
A principal objective of the invention is to provide improved systems and methodologies to form larger and deeper lesions using curvilinear ablating elements.
One aspect of the invention provides a device and associated method for creating large lesion patterns in body tissue. The device and method use a support element having a curved region to peripherally contact a tissue area. The support element carries at least two energy emitting zones on the curved region, which are mutually separated across the contacted tissue area. The mutual separation between the zones across the contacted tissue area is sufficient to create, when the zones simultaneously emit energy, an additive heating effect to form a continuous lesion pattern in the contacted tissue area that spans across the contacted tissue area.
In one embodiment, a continuous energy emitting electrode is present on the curved region of the support element.
In another embodiment, the two energy emitting zones comprise non-contiguous energy emitting segments on the curved region mutually separated across the contacted tissue area.
Another aspect of the invention provides a device and associated method for ablating body tissue using a support element having a region curved along a preselected radius to peripherally contact a tissue area. The device and method include at least two energy emitting zones on the curved region, which are mutually separated across the contacted tissue area. The radius of curvature of the curved region is equal to or less than about 3.5 times the smaller of the diameters of the first and second zones. When the zones are conditioned to simultaneously emit energy, a continuous large lesion forms that spans across the contacted tissue area.
In one embodiment implementing this aspect of the invention, the device and method employ a continuous energy emitting electrode on the curved region of the support element.
In another embodiment that implements this aspect of the invention, the two energy emitting zones comprise non-contiguous electrode segments separated on the curved region of the support element. In a preferred embodiment, the length of each zone is greater than about 5 times the diameter of the respective zone.
Another aspect of the invention provides a device and associated method for ablating body tissue that also use a curved support element that peripherally contact a tissue area. The device and method include at least two non-contiguous energy emitting zones on the curved region, which are mutually separated across the contacted tissue area.
According to this aspect of the invention, the separation between the zones across the contacted tissue area is equal to or less than about 7 times the smaller of the diameters of the first and second zones. When the zones are conditioned to simultaneously emit energy, a continuous large lesion is formed spanning across the contacted tissue area.
In one embodiment implementing this aspect of the invention, the device and method employ a continuous energy emitting electrode on the curved region of the support element.
In another embodiment that implements this aspect of the invention, the two energy emitting zones comprise non-contiguous electrode segments separated on the curved region of the support element. In a preferred embodiment of this aspect of the invention, the length of each zone is equal to or less than about 5 times the diameter of the respective zone.
Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.